World War Z Directed by Marc Forster Duration: November 2010 – February 2012 Over the course of a year and four months Previs Director Daniel Gregoire chased Zombies from Los Angeles, to London, Malta, Budapest and Glasgow with a portable V CAM System in an effort to save the world from the zombie hordes! While back at home base supervisor Bradley Alexander and team barricaded themselves into the office and provided tactical support using motion capture, virtual camera, MotionBuilder and Maya to save the production with killer scenes of havoc wrought across the planet! After most of the world retreated to safe havens and turned it’s eye to offense HALON fielded the effort with a Postvis team lead by Postvis Supervisor Michael Jackson. Together with his team, he killed plate after plate so editorial could move the front line forward. HALON Team Credits Previs Director: Daniel D. Gregoire Previs Supervisor: Bradley Alexander Previs Artists: Andrew Greenlee AJ Briones Alex Menard Ben Shupe Benny Vargas Brian Magner Bryan Chojnowski Thomas Chao Tung Huang Clint G. Reagan Euisung Lee Jerry Zigounakis Joe Henderson Kenny Digiordano Long-Hai Pham Nina Huynh Paolo Joel Ziemba Richard Perry Stephen Camardella Stephen Deane Tefft Smith II Travis Yee

• published: 27 Sep 2013
• views: 4499

Three visualizations were sent to us recently by our friends and colleagues at NASA GSFC, Ernie Wright and his talented visualization team of animators. This is number 1 of 3. On Monday, August 21, 2017, the Moon will pass in front of the Sun, casting its shadow across all of North America. This will be the first total solar eclipse visible in the contiguous United States in 38 years. The Moon's shadow can be divided into areas called the umbra and the penumbra. Within the penumbra, the Sun is only partially blocked, and observers experience a partial eclipse. The much smaller umbra lies at the very center of the shadow cone, and anyone there sees the Moon entirely cover the Sun in a total solar eclipse. In the animation, the umbra is the small black oval. The red streak behind this oval is the path of totality. Anyone within this path will see a total eclipse when the umbra passes over them. The much larger shaded bullseye pattern represents the penumbra. Steps in the shading denote different percentages of Sun coverage (eclipse magnitude), at levels of 90%, 75%, 50% and 25%. The yellow and orange contours map the path of the penumbra. The outermost yellow contour is the edge of the penumbra path. Outside this limit, no part of the Sun is covered by the Moon. The numbers in the lower left corner give the latitude and longitude of the center of the umbra as it moves eastward, along with the altitude of the Sun above the horizon at that point. Also shown is the duration of totality: for anyone standing at the center point, this is how long the total solar eclipse will last. Note that the duration varies from just 2 minutes on the West Coast to 2 minutes 40 seconds east of the Mississippi River. About Accuracy You might think that calculating the circumstances of an eclipse would be, if not easy, then at least precise. If you do the math correctly, you’d expect to get exactly the same answers as everyone else. But the universe is more subtle than that. The Earth is neither smooth nor perfectly spherical, nor does it rotate at a perfectly constant, predictable speed. The Moon isn’t smooth, either, which means that the shadow it casts isn’t a simple circle. And our knowledge of the size of the Sun is uncertain by a factor of about 0.2%, enough to affect the duration of totality by several seconds. Everyone who performs these calculations will make certain choices to simplify the math or to precisely define an imperfectly known number. The choices often depend on the goals and the computing resources of the calculator, and as you'd expect, the results will differ slightly. You can get quite good results with a relatively simple approach, but it sometimes takes an enormous effort to get only slightly better answers. The following table lists some of the constants and data used for this animation. Earth radius 6378.137 km Earth flattening 1 / 298.257 (the WGS 84 ellipsoid) Moon radius 1737.4 km (k = 0.2723993) Sun radius 696,000 km (959.634 arcsec at 1 AU) Ephemeris DE 421 Earth orientation earth_070425_370426_predict.bpc (?T corrected) Delta UTC 68.184 seconds (TT – TAI + 36 leap seconds) A number of sources explain Bessel’s method of solar eclipse calculation, including chapter 9 of Astronomy on the Personal Computer by Oliver Montenbruck and Thomas Pflager and the eclipses chapter of The Explanatory Supplement to the Astronomical Almanac. The method was adapted to the routines available in NAIF's SPICE software library. The value for the radius of the Moon is slightly larger than the one used by Fred Espenak and slightly smaller than the one used by the Astronomical Almanac. The Sun radius is the one used most often, but see figure 1 in M. Emilio et al., Measuring the Solar Radius from Space during the 2003 and 2006 Mercury Transits for a sense of the uncertainty in this number. Both the elevations of locations on the Earth and the irregular limb of the Moon were ignored. The resulting small errors mostly affect the totality duration calculation, but they tend to cancel out—elevations above sea level slightly lengthen totality, while valleys along the lunar limb slightly shorten it. The effect on the rendered images is negligible (smaller than a pixel). Another minor complication that's ignored here is the difference between the Moon's center of mass (the position reported in the ephemeris) and its center of figure (the center of the disk as seen from Earth). These two centers don't exactly coincide because the Moon's mass isn't distributed evenly, but the difference is quite small, about 0.5 kilometers.

• published: 10 Sep 2015
• views: 29